1. Field of the Invention
The present invention relates to a method for generating a current differential protection supernode based on an electrical topology of a regional distribution network, which belongs to the fields of automation of electrical power systems and relay protection.
2. Background of the Invention
In order to improve the power supply reliability of distribution systems, loop network structure has been adopted in the existing distribution network. Under the loop network structure, however, it is difficult to tune setting values protected by feeding lines of a substation and main lines of a distribution network in which the main protection object is over-current protection, and the setting values can not match the time delay. Moreover, the introduction of distributed power supply changes the topological structure of the original distribution network from signal power supply radiation shape to multi-power supply network structure, which has a great effect on the relay protection of the distribution network. Based on the above reasons, it is necessary to design a new protection strategy appropriate for continuously developed distribution network.
The application of optical fiber composite cable technique provides a good basis for construction of optical fiber communication channels for the distribution network. The quickly developed network technique satisfies the increasing requirements for transmission ability, safety and reliability of the network. IEC 61850 standard has been maturely applied to the intelligent substation. With the fast development of computer technology and information technology, the integration of the hardware platform for relay protection increases, and the reliability thereof improves greatly. The applications of these advanced technologies establish the basis of information sharing and intelligent distribution network, and also provide the possibility for new principle, research of new solutions and implementations. Therefore, the new relay protection of the distribution network shall face the whole regional distribution network, instead of a single power supply line. The design idea of centralized network protection is already to be implemented.
Since it is not necessarily configured with three-phase PT, or only configured with signal-phase PT at positions to be protected in each supply section of the distribution network, considering the selection and sensibility, the protection based on a current differential principle is the most suitable new relay protection of the distribution network. However, due to cost, maintenance, etc., it is improper to configure the current differential protection at each supply line section of the distribution network. Thereby, the centralized differential protection facing the regional distribution network is the most optimal solution. The function of the centralized differential protection is to accurately and quickly locate and isolate the fault sections of the distribution network supply line, and the protection operation time can be improved to 50 ms. The centralized protection system of the regional distribution network may be consisted of one centralized protection apparatus and several distributed intelligent terminals. The centralized protection system is configured with a whole-line quick-action protection-differential protection. The distribution terminals collect and upload analogy data on the spot, and configure the fundamental backup protection. The centralized protection system of the distribution network can accurately locate and quickly isolate the fault within the distribution network system, reduce the probability of power cut in the non-fault lines, reduce the coverage of power cut, quickly reconstruct and self-healing the distribution network, and solve the effect of the distributed access system on the distribution network protection.